Protection of plant life from frost damage



United States Patent ice 3,045,394 PRQTECTION 0F kLANT, LIFE FRQM FRQST DAMAGE Thomas H. Conifer, Jackson, Miss, assignor to Dumas Milner Corporation, Jackson, Miss, a corporation of Mississippi No Drawing. Filed Mar. 9, 1959, Ser. No. 797,875 12 Claims. (Ci. 47--2) This invention relates to the protection of plant life from damage caused by freezing temperatures or frost.

Frost or freezing temperature causes heavy economic losses in many forms of plant life. The art has long sought a simple and inexpensive method of preventing or minimizing frost damage to plant life. Prior art methods, including preventing heat radiation by the use of smoke, heating of the air by fuel burners and providing cover for plants in the form of paper or cloth shields, have been found expensive and often undependable.

Accordingly, it is among the objects of this invention to provide simple, inexpensive and effective methods of protecting living plants from frost damage.

Another object of the present invention is to provide methods and compositions for protecting plants from frost damage which involve the use of conventional spraying methods and apparatus.

A further object of the invention is to provide methods and compositions for protecting plants from frost damage which afford protection for extended periods of time and which are efiective on all economic plant life subject to frost damage without regard to the plan-t size or the size or topography of the site on which the plants are grown.

Other objects and advantages of the invention will be apparent to those skilled in the art from the following description.

The term frost damage as used herein designates damage due to subfreezing temperatures, whether or not it is accompanied by the feathery ice crystal formation commonly known as frost or hoar frost. Hence, frost damage, as used herein, includes damage arising from temperatures lower than 32 R, which may be accompanied by snow, sleet, frost or black frost, i.e. subfreezing temperatures accompanied by low relative humidity whereby no ice crystals are formed.

The method of this invention for protecting living plants from frost damage generally involves applying to the plant a polymer of N-vinyl-2-pyrrolidone. The vinylpyrrolidone polymer is preferably in a non phytotoxic carrier, such as water, oil-in-water emulsions, glycols, oils, or other liquid carriers which are not toxic to plant life. The vinylpyrrolidone polymer is preferably applied by spraying.

The active ingredient, a polymer of vinylpyrrolidone may be a homopolymer of N-vinyl-Z-pyrrolidone, i.e. polyvinylpyrrolidone or PVP as it is commonly known, or a copolymer of N-vinyl-2-pyrrolidone. The latter are copolymers with polymerizable unsaturated compounds including vinyl acetate, vinyl chloride, styrene, alpha-methyl styrene, maleic anhydride, dialkyl maleates or dialkyl fumarates containing 4-12 carbon atoms in the alkyl group, vinyl ethers such as isobutyl vinyl ether, acrylic and methacrylic acids and alkyl esters thereof, acrylonitrile, acrylamide, and vinyl alcohol esters of fatty acids such as vinyl laurat'e and vinyl stearate.

The copolymers of N-vinyl-2-pyrrolidone with such unsaturated compounds may contain from about 10 percent to 90 percent by weight of vinylpyrrolidone and 90 percent to 10 percent by weight of copolymerizable unsaturated monomer. In addition, ternary copolymers of'vinyl pyrrolidone, including those with isobutyl vinyl ether and acrylonitrile may be utilized, In general, copolymers con- 3,045,304 Patented July 24-, 1962 taining a higher percentage of vinylpyrrolidone are more Water soluble or water compatible than those containing relatively less vinylpyrrolidone. Homopolymers of vinylpyrrolidone are completely water soluble.

Homopolymers and copolymers of N-vinyl-Z-pyrrolidone having a wide range of molecular weights are useful in protecting plants against frost damage. Polyvinylpyrrolidones having average molecular Weights ranging from about 40,000 to over 360,000 have been found to be effective. Copolymers of vinylpyrrolidone having a similar range of molecular weights have been found useful in protecting plants against frost damage.

It has been found that sprays containing from about 0.01 percent to about 2 percent of vinylpyrrolidone polymer are effective in preventing frost damage to plants. Larger quantities are uneconomical although they are not deleterious to most plants. The polymer, in the form of a solution, emulsion or dispersion, is sprayed onto the leaves, stalks, fruit, buds, flowers, etc. of living plants and is effective to protect the coated parts against frost damage.

The carrier for the polymer must be one which is not toxic to plants. Water alone may be used for water-soluble polymers, but it is preferred to employ a carrier which adheres to plants more readily, such as an oil-in-water emulsion or the like. Such emulsions are Well-known in the art as carriers for insecticides or herbicides and include so-callecl plant-spray oils (refined mineral oils of a wide range of viscosities) water, and a suitable emulsifier or surface-active agent. The surface-active agent in such emulsions must not, of course, be phytotoxic in the concentrations used, and may be anionic, non-ionic, or cationic, to suit particular compositions. Additional carriers include glycols, glycerol, glycol ethers and the like.

While not intending to be bound by any particular theory of operation, it appears that the vinylpyrrolidone polymer penetrates into the plant cell structure and lowers the freezing point of the cell fluids, thereby enabling the plant to withstand temperatures below freezing without damage.

The following examples illustrate the invention. All parts are by weight.

Example I Percent Polyvinylpyrrolidone (mol. wt. 40,000) 0.5 Water 99.5

, of untreated control plants sustained severe frost damage when subjected to the same conditions.

In practice, aqueous solutions of vinylpyrrolidone polymers are prepared in concentrated form, and diluted at the time of use to the proper concentration in the range of 0.01 percent to 2'percent by weight. Aqueous solutions of PVP containing 0.03 percent, 0.1 percent, 0.25 percent, 1 percent and 2 percent, of PVP were found effective as frost damage preventives.

Example 11 Percent Copolyrner of 65% vinylpyrrolidone and 35% vinyl acetate 10.0 Nonyl phenol-ethylene oxide condensate (emulsifier 5.0 Water 85.0

Portions of the above were diluted with water to give compositions containing 0.1%, 0.5% and 1% of polymer.

The resulting sprays afforded protection against frost damage when sprayed on plants as in Example I.

3 Example 111 Percent Copolymer of 60% vinlpyrrolidone and 40% vinyl chloride 20.0 Glycerol 50.0 Sorbitan monolaurate (emulsifier) 10.0 Water 20.0

Example I V Percent Copolymer of 50% vinylpyrrolidone and 50% methyl acrylate 20.0 C-dodecyl betaine (cationic surface-active agent) 5.0 Hexylene glycol 5.0 Plant spray oil 90-110 USS 40.0 Water 30.0

Portions of the above were diluted with water to give concentrations of 0.05%, 0.15%, 0.75% and 1%, were effective in protecting plants against frost damage.

Example V Percent Copolymer of 40% vinylpyrrolidone and 60% acrylonitrile 15.0 "l riethanolamine lauryl sulfate 5.0 Kerosene 60.0

Water 20.0

The above, when diluted with water to give polymer concentrations of 0.05% to 2% were effective frost damage preventives.

Example VI Percent Polyvinylpyrrolido'ne (360,000 mol. wt.) 0.5 Tetraethylene glycol 10.0 Sorbitan monooleate ethylene oxide condensate 0.5 Water 89.0

The above was an effective frost damage preventive.

Example VII Percent Polyvinyl pyrrolidone (40,000 mol. wt.) 0.5 Ethanol 20.0 Trichlorofiuoromethane 55.0 Dichlorodifluoromethane 24.5

The above was packaged in a pressurized aerosol container to give a self-spraying package for small applica- The above was packaged in a pressurized aerosol container and used as in Example VII.

Examples lX-Xll The following compositions were prepared:

Percent Polymer 0.5 Tall oil-ethylene oxide condensate 2.0 Mineral plant spray oil 20.0 Water 77.5

The polymers in each of the examples consisted of the following:

Example IX Copolymer of 40% vinylpyrrolidone and 60% vinyl stearate Example X Copolymer of 60% vinylpyrrolidone and 40% styrene Example XI Copolymer of 70% vinylpyrrolidone and 30% diethylhexyl maleate Example XII Copolymer of 20% vinylpyrrolidone and vinyl acerate The above sprays were effective in protecting plants against frost damage.

The compositions of Examples I-XII have been tested by application to living plants subjected to frost and to temperatures below freezing occurring from actual atmospheric conditions. In such tests ornamental plants and shrubs were treated and marked with adjacent plants of the same varieties left untreated as controls. In such tests the composition did not harm the treated plants and they were observed to be protected from frost and freezing damage which injured or killed adjacent control plants.

Further tests upon living plants Were conducted by constructing an enclosed insulated chamber which could be chilled by suitable refrigeration to obtain frost or freezing conditions (depending upon the humidity). Plants to be tested were obtained from a nursery and in each test at least two substantially identical control plants were selected, one (low temperature control) being subjected to the same low temperature conditions as the treated plant and the other held at room temperature to furnish a basis 0 for comparing the tested plants with an untested standard.

A typical test Was conducted upon Pedilanthus, a succulent, frost-susceptible plant, by selecting four well-developed specimens, one was subjected to the low temperature test without treatment with the protective composition, two were subjected to the low temperature test after being treated by the application of a light spray of the protective composition to form a film upon the plant surfaces, and one specimen was held at room temperature. The low temperature test began with the chamber at 75 F. It was gradually chilled to a uniform temperature of 30 F. and this temperature was maintained for three hours. The plants treated with the protective composition of the present invention showed traces of frostburn, but only on the tips and edges of the leaves. The vegetative parts, leaf surfaces, stems, etc., showed no evidence of frost damage. The plant that was untreated and subjected to the same frigid conditions sustained severe frost damage to all vegetative parts other than the base of the main stems. It was almost completely devoid of sound leaves, and the apex of every shoot was killed back for a distance of 4 to 6 inches.

Further tests using substantially the same procedure were conducted using the composition of Example I, and specimens of a number of species of plants, including avocado, orange, lemon, caladium, Allamanda and grapefruit. In a series of tests in which the tested plants were maintained at 29 F. for at least an hour, specimens of avocado, coffee plant and Allamanda were completely protected by applying a light spray of the composition of the present invention to the surfaces of the plant to form a thin film thereon so that no damage was observed. The low temperature control plants all showed varying degrees of frost damage to the leaves.

In further similarly conducted tests of the composition of Example I, using, simultaneously, specimens of avocado, coffee plant, grapefruit and Pedilanthus, a temperature of 26 F. was maintained for one hour with the plants kept for more than four hours below freezing. In this test the control specimen of Pedilanthus was completely wilted and tissues blackened whereas the treated specimen showed only a trace of wilt and no serious damage. The avocado and coffee plants which were not treated showed leaf damage and the treated specimens showed only a slight trace of wilt upon a very few apex leaves. The grapefruit specimen without treatment was only slightly damaged and the treated specimen showed no damage.

The test at 26 F. was repeated using the same species of plants and adding orange plants, and the temperature at 26 F. was maintained for three hours. The results were substantially the same, with all untreated plants showing prominent damage. The treated plants were only slightly damaged by wilt or burn of some young growth and leaf tips.

Similarly, the compositions of Examples II-XII were tested at temperatures ranging down to 24 F. Compositions containing polymer in the range of 1-2 percent were completely effective at 24 F.; lesser amounts of polymer protected plants at somewhat higher freezing temperatures. In all the tests, there was no evidence of injury to the plants as a result of the application of the compositions.

It has been found that the compositions containing an oil give the most lasting protection. Water solutions of PVP are effective, however, provided the film is not washed ofi the plant by rain, etc.

While the invention has been described in terms of certain examples, such examples are to be considered illustrative rather than limiting, and it is intended to cover all further modifications and embodiments that fall within the spirit and scope of the appended claims.

I claim:

1. The method of protecting living plants from frost damage Which comprises applying to the plant a liquid film of a polymer of N-vinyl-Z-pyrrolidone in a nonphytotoxic carrier.

2. The method set forth in claim 1 wherein said polymer is a homopolymer of N-vinyl-Z-pyrrolidone.

3. The method set forth in claim 1 wherein said polymer is a copolymer of N-vinyl-Z-pyrrolidone with an ethylenically unsaturated polymerizable monomer.

4. The method set forth in claim 1 wherein said carrier is water.

5. The method set forth in claim 1 wherein said earrier is an oil-in-water emulsion.

6. The method set forth in claim 1 wherein said carrieris an aliphatic polyhydric alcohol.

7. The method of protecting living plants from frost damage comprising applying to the plant a liquid film of 0.01% to 2% by weight of a polymer of N-vinyl-2- pyrrolidone in a non-phytotoxic carrier.

8. The method set forth in claim 7 wherein said polymer is a homopolymer of N-vinyl-2pyrrolidone.

9. The method set forth in claim 7 wherein said polymer is a copolymer of N-viny1-2-pyrrolidone with vinyl acetate.

10. The method set forth in claim 7 wherein said carrier is an oil-in-water emulsion.

11. The method set forth in claim 7 wherein said carrier is an aliphatic polyhydric alcohol. I

12. The method of protecting living plants from frost damage comprising applying to the plant a liquid film of an aqueous solution containing 0.01% to 2% by weight of polyvinylpyrrolidone.

References Cited in the file of this patent UNITED STATES PATENTS 1,995,853 Hunsaker Mar. 26, 1935 2,185,663 Greenstreet Jan. 2, 1940 2,875,555 Thiegs Mar. 3, 1959 FOREIGN PATENTS 159,544 Australia Nov. 1, 1954 797,992 Great Britain July 9, 1958 OTHER REFERENCES Agricultural Chemicals, Volume 11, No. 1, pages 61 and 62, article Polyvinylpyrrolidone-Iodine Shows Promise as Agricultural Chem. published January 1956.

Condensed Chemical Dictionary, Fifth Edition, published by Reinhold (N.Y.), 1956. Pages 345 and 1130 relied on.

DiGiacomo, Aerosols for Packaging Cosmetic published May 1957 in American Perfumer and Aromatics (magazine), Vol. 69, No. 5, pages through Chemical Abstracts, Vol. 44, published 1950, col. 10,059a', article Retarding Action of Polyvinylpyrrolidone on Some Organs of Plants. 

1. THE METHOD OF PROTECTING LIVING PLANTS FROM FROST DAMAGE WHICH COMPRISES APPLYING TO THE PLANT A LIQUID FILM OF A POLYMER OF N-VINYL-2-PYRROLIDONE IN A NONPHYTOTOXIC CARRIER. 